An example of method for manufacturing a bent hollow pipe such as a suspension arm for a vehicle includes the manufacturing method described in Patent Literature 1. This method is a method for pressing a flat plate, which is a material, into ultimately a two-dimensionally bent hollow pipe through press-forming in a stepwise manner using multiple forming dies, and thus the bent hollow pipe can be formed without using a core. In this method, first, flange portions extending in directions away from each other are formed in a flat plate, subsequently, both of the flange portions are bent in a press direction so as to be in substantially parallel with each other, and thereafter, both of the flange portions are brought into contact with each other along the inner wall of a forming die, so that a pipe is formed.